1. Field of the Invention
This invention relates to motor driven cameras capable of motorized shutter charging, film winding and rewinding.
2. Description of the Prior Art
Recently, as the technique of motorizing the camera has advanced, cameras capable of motorized film winding and rewinding name been proposed. This kind of camera is constructed in such a way that the driving torque transmission from the electric motor to the takeup spool is provided with a change-over mechanism or clutch at a cross point to another transmission to the supply spool so that only one motor is used for performing the winding and rewinding operations as the change-over mechanism selects either one of them.
In general, the winding and rewinding systems of the camera lie at opposite ends of the camera body with the lens intervening therebetween. For example, in the single lens reflex camera, as viewed from the holding position of the camera, on the right hand side there is the winding mechanism, and on the left hand side is the rewinding mechanism. Also, the right hand end portion of the camera housing contains the electric motor adjacent the winding mechanism. A recent trend is to form the right hand end portion protruding forward to accommodate that motor and to make it usable as a grip with the advantage of improving steadiness while holding the camera. This is widely used even in single lens reflex cameras. In order to provide in such a motoried winding camera a motorized rewinding capability, a change-over mechanism must be arranged between the electric motor and the winding and charging system, and the driving torque through the change-over mechanism must be transmitted to the opposite side of the mirror box on which the rewinding mechanism lies. This transmission is usually in the form of a train of gears. Because of the limitations on the width of the camera housing, and because the speed reduction rate is in a range determined by the load and the output of the motor, the required number of gears from the output shaft of the motor to the output terminal end at the hub of the film cassette is about 12 to 16. For such a large number of gears in successive connection, the transmission efficiency is very low, or about 20 to 30%.
Also there is prior art proposing the use of a motor driven winding device for charging the shutter, resetting the lens drive mechanism, and carrying out other operations necessary to make the camera ready for the next exposure, or in other words, performing all the charging operations by one motor. Of these charging operations, the shutter charging and the lens charging operations are always with almost stable loads independent of variations of the ambient temperature. But, as to the film winding operation, its load varies depending on the lot number for production of films, the types of film, and the ambient temperature. It is known that the minimum and maximum values of that load differ by about a factor of 5 from each other. In such a way, according to the prior known proposals, the mechanisms of different character were charged at a time. Therefore, stress was applied on the motor and the battery, giving rise to a problem preventing charging with good efficiency.